Can one daven Shemoneh Esrei on a city bus?

Chazal gave a special dispensation for a traveler to daven Shemoneh Esrei while he is traveling, even when he is not facing the proper direction for tefilah. They were concerned that if a traveler was compelled to stop, he would be distressed and his kavana would be disturbed. This leniency can only be applied on a case-by-case basis, depending upon whether one’s concentration would be disturbed by stopping to daven. One who is traveling ahead of his entourage and needs to wait for them anyway must pause to daven. Some poskim say that a person who is traveling on a local city bus must disembark before davening. They explain that waiting for another local bus is not overly distressing, so getting off the bus would not disturb a person’s kavana. It is forbidden to daven while driving a car. Since a driver must focus on his task, he will not be able concentrate on davening. In addition, multi-tasking while driving is dangerous.

סצ"ד ס"ד ס"ק י"ב וט"ז ביאורים ומוספים דרשו 10

Should an airplane passenger stand for Shemoneh Esrei?

A person who is traveling on a boat or wagon and is afraid to stand up may daven Shemoneh Esrei sitting down. He should, however, attempt to stand at the points where one is supposed to bow and where one is supposed to take three steps back. If a merchant is concerned that his merchandise may be stolen, he may also daven while sitting down. Some contemporary poskim compare airplane travel to traveling by boat or wagon. If it is difficult for an airplane passenger to daven while standing, he should daven sitting down and stand up at the above-mentioned points in his tefilla. The poskim explain that standing may be difficult and would make it difficult to concentrate. Others reject the comparison and hold that one must daven while standing in a section of the plane where he will not be disturbed.

ס"ה ס"ק י"ח ביאורים ומוספים דרשו 16

Can one lean during Shemoneh Esrei?

One may not daven while leaning on another object or person. Standing while leaning is not considered standing. Leaning in a way that one is still self-supporting is not an issue. Alternatively, one must daven with a sense of awe, and leaning is not consistent with such a feeling. According to this view, even a slight lean would be forbidden. Under pressing circumstances, one may be lenient. A sick or elderly person may daven sitting down. If necessary, someone in this category may even daven while lying in a bed. If it is difficult to stand for the entire Shemoneh Esrei, one should stand as long as possible and then sit down.

ס"ו וס"ט ס"ק כ' וכ"ב ביאורים ומוספים דרשו 21

• If one began Shemoneh Esrei facing the wrong direction, he should not move his feet to change direction. Instead, he should turn his head in the appropriate direction. If he is in shul together with a minyan, however, he may turn to face the same direction as the rest of the tzibur.

• The poskim say that it is not necessary to face northward or southward for the entire davening. Instead, at the time that one is davening for wealth he should face northward, and when he is requesting wisdom he should face southward.

• Since many European countries are northwest of Eretz Yisroel, many poskim hold that the proper direction to face for davening is southeast. 

• May one daven in a room with idols?

• What is the proper way to prepare for Shemoneh Esrei?

• Why do we stand with our feet together during Shemoneh Esrei?